Process for testing a compressor or a combustor of a gas turbine engine using a large compressed air storage reservoir

ABSTRACT

A process for testing a combustor or a compressor of a gas turbine engine, where a large volume of compressed air is stored in a large reservoir of at least 10,000 m3 such as an underground storage cavern, compressed air from the storage reservoir is passed through an air turbine to drive a compressor to produce high pressure and temperature compressed air, and where the compressed air can be discharged into a combustor and burned with a fuel for testing of the combustor under simulated conditions of a real gas turbine engine.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation-In-Part of U.S. patent applicationSer. No. 14/008,308 filed on Nov. 13, 2013 which claims the benefit toPCT/US2012/029231 filed on Mar. 15, 2012; which claims the benefit toU.S. Provisional Application 61/468,771 filed on Mar. 29, 2011 and U.S.Provisional Application 61/561,956 filed on Nov. 21, 2011 and U.S.Provisional Application 61/569,378 filed on Dec. 12, 2011 and U.S.Provisional Application 61/587,022 filed on Jan. 16, 2012.

GOVERNMENT LICENSE RIGHTS

None.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to an apparatus and a processfor testing a component of a gas turbine engine, especially for a largeaero gas turbine engine, and for a process for testing a largeindustrial gas turbine engine that require large flow capacity andpressure ratios.

2. Description of the Related Art Including Information Disclosed Under37 CFR 1.97 and 1.98

A large frame heavy duty industrial gas turbine (IGT) engine istypically used to drive an electric generator and produce electricalenergy. These engines can produce over 200 MW of electric power. An IGTengine will have a compressor with multiple rows or stages of rotorblades and stator vanes, a combustor with multiple can combustorsarranged in an annular array (also referred to as a can annularcombustor), and a turbine with multiple rows of rotor blades and statorvanes. An aero engine typically has an annular combustor instead ofmultiple can combustors arranged in an annular array as in the IGTengines.

The single largest hurdle to introducing new technologies into largeframe power generation gas turbine engines or aero engines is the riskthat the new technology may fail during operation of the engine andresult in tens of millions of dollars in equipment damage and possiblythe cost of replacement electricity during the down time of the powerplant. Thus, an owner of one of these engines is very reluctant to allowfor the use of the engine in testing a new technology. As a result, itis very difficult to introduce new technologies into a utility powergeneration plant. Therefore most power generation manufacturers havetest facilities to test as much as possible the components prior togoing into production. Unfortunately the cost of test facilities andrunning the tests prohibits extensive testing and usually only allowsfor infant mortality issues to be discovered prior to installation of anew gas turbine engine at the utility site.

Testing a large IGT engine as a whole or testing a part or component ofthe engine is both very expensive and very difficult and complex. When alarge engine is tested, the power generated must be dissipated. Onemethod of dissipating the energy produced is to drive an electricgenerator and dump the electrical power produced. The excess electricalpower produced during testing can be supplied back into the electricalgrid. However, this can become a real problem with the electric powercompany. Since the engine testing might only last for a few hours,supplying this large amount of electricity to the grid for a few hoursand then stopping causes real problems with the power company,especially if the power suddenly stops due to a problem during the testwhich trips the gas turbine engine offline.

Another problem with testing aero engines or large frame engines is thatthe cost to test is very high. In some IGT engine test beds, instead ofusing an electric generator to supply the resistance load, a water breakor electrical heater resistors can be used to dissipate the loadproduced by the engine. These means of dissipating the load hasadvantages over the electrical power production described above in thatthe disturbance to the electrical grid is not produced. However, thedisadvantage is that all of the energy produced is lost.

In a power plant that uses an IGT engine to drive a generator andproduce electrical power, the electrical power required by the localcommunity cycles from high loads (peak loads) to low loads such asduring cool days or at night. One process to match electric supply withdemand of an electrical power plant is to make use of compressed airenergy storage (CAES) system. At low loads, instead of shutting down anengine, the engine is used to drive a compressor instead of an electricgenerator to produce high pressure air that is then stored within anunderground cavern such as a salt mine cavern. A large amount ofcompressed air is collected and then used to supply the engine duringthe peak loads.

When testing a gas turbine engine such as a large industrial engine oran aero engine or a component of one of these engines, the engine orcomponent needs to be tested at different operating condition other thanjust the steady state condition. Engine partial load conditions must betested for and therefore requires different fuel and compressed airflows. Also, the loads on the engine vary during the testing processfrom a full load at the steady state condition to partial loads. Thus,the amount of energy dissipated varies during the engine testingprocess.

Testing of a component of a large frame heavy duty industrial gasturbine engine is also required. Each of the components of an enginerequires testing. The compressor, the combustor or the turbine can betested as a separate unit from the engine. For example, in the testingof a combustor, a large volume of compressed air at high pressure(15-100 bars) is required to be supplied to the combustor to be burnedwith a fuel for testing. One or more compressors are required to producethis large volume of compressed air. Thus, a large electric motor with apower output of 20-200 MW and over is required to drive the compressoror compressors. Thus, testing of combustors requires a large capitalexpense and maintenance requirements.

When a component of a large industrial or aero gas turbine engine is tobe tested, such as a combustor module or a turbine module or acompressor module, the entire engine is operated just to test that onecomponent module. The entire engine is required to be operated in orderto produce the conditions required to test that component module. Thus,it is very costly to test a single component module in a gas turbineengine when the entire engine is to be operated. Also, during operationof the gas turbine engine for testing one of the component modules suchas a turbine module, a load is connected to the turbine in order tocreate a resistance during the testing process. As described above inthe entire engine testing process, this load is typically lost ordifficult to dissipate.

In testing of a compressor module, the compressed air produced duringthe testing process is wasted due to the high cost of storing thecompressed air for future use. Thus, the energy produced in the testingprocess of a compressor module is also wasted.

An airfoil that requires a high Mach number of air flow for testing istypically supplied with compressed air from a compressed air storagetank that is relatively small and very heavy in construction towithstand the high pressures. Because of the limited size of thecompressed air tank, the testing period is on the order of a few secondswhich limits the accuracy of the test data and the types of data thatcan be measured.

Recently, several gas turbine Original Equipment Manufacturers (OEM's)have indicated a need for combustion research capability that farexceeds the flow capacity and pressure ratios of existing facilities.This requirement for new combustion research facilities is motivated inthe first instance by the need to design more environmentally benign gasturbines producing much reduced greenhouse gas emissions using hydrogenor, in the interim, blended hydrogen fuels. This requirement coincideswith the rust-out of existing OEM combustion research facilities and theneed to relocate existing facilities away from urban areas.

There is a pressing market requirement for a combustion researchfacility having significantly increased air mass flow rate andcompression ratios than currently exist. The combustion researchcapacity and capability sought is necessary for next generationindustrial gas turbines that will employ much higher pressure ratiosthan today's engines and will burn a variety of gaseous and liquid fuelswith ever reducing greenhouse gas emissions. Hydrogen produced fromenvironmentally benign coal gasification is a key green target for theUS government, based on extensive USA coal reserves and energy securityagenda.

The National Research Council Institute for Aerospace Research (IAR) GasTurbine Laboratory (GTL) already performs similar combustion researchand technology demonstration. GTL R&TD is on both conventional andalternative fuels but at lower pressure ratios and air mass flow ratesthan are required for future technology development, demonstration andvalidation. The minimum facility air mass flow rate and operatingpressure ratio that would be sufficient for this facility would be 150lb/sec at a pressure ratio of 60:1. This requires a compressor drivepower of 80 MW although redundancy would be a highly desirable facilityattribute. The Compressor Institute design standard dictate that no morethan 40 MW of compressor capacity be driven by one shaft. This meansthat at least two 40 MW gas turbines would be required, however, it maybe prudent to use more than two drive gas turbines to enable costeffective delivery of less than one engine size class. This size testfacility is estimated to cost around $200 Million. A more desirablefacility capacity would provide 300-550 lb/sec of air at a minimumpressure ratio of 60:1, but would require a compressor drive capacity ofaround 150 MW. A full capacity facility would deliver 550 lb/sec of airat the 60:1 pressure ratio, but with a capital investment in excess of$600 Million.

Transient blow down testing is a technique that has been used for manyyears in aerospace testing. This technique is used to reduce the sizeand cost of compression and vacuum pumps required to develop theconditions required for a test. For example, a compressor can be run fordays or longer to fill a tank to very high pressure and/or a vacuumchamber to very low pressure. The gas is then released for testing.Depending on the mass-flow required during the test, the actual testtime can vary from milliseconds up to many minutes. While the cost ofthe compression and vacuum equipment is kept low using the blow downfacility idea, the cost of the pressure and vacuum tanks become verylarge. NASA Langley has some of the largest high pressure tanksavailable for testing to create very high Mach number flows.

BRIEF SUMMARY OF THE INVENTION

An apparatus and process for testing a large aero or industrial gasturbine engine or a single component of an engine, where the enginetesting facility is established close to a compressed air energy storage(CAES) facility or to an underground cavern that can store compressedair so that the engine during testing can supply the undergroundcompressed air storage reservoir with compressed air, or the undergroundcompressed air storage reservoir can supply the engine or componentmodule testing facility with compressed air for the testing of an engineor an engine component module such as a compressor module or a combustormodule or a turbine module.

For testing of an IGT engine, the turbine is connected to drive acompressor so that the load from the engine during testing is used todrive the compressor to produce compressed air that is then storedwithin the storage cavern or CAES facility for use in peak powerproduction later or for other engine testing requirements. Thus, nodisruption to the electric grid is produced, and no energy from theengine testing is wasted. Compressed air from the storage cavern or CAESfacility can be burned with a fuel to produce the hot gas stream fortesting within the turbine, and the turbine can be used to drive acompressor to resupply the storage cavern or CAES facility for lateruse.

In the testing of a single engine component, such as a combustor or aturbine, the large volume and high pressure compressed air can besupplied from the CAES facility or storage cavern for use in testing thecomponent. Therefore, a large capital investment in equipment and abuilding is not required since the infrastructure already exists at theCAES power plant.

Because of the use of an underground CAES facility or storage cavern forthe supply of compressed air for testing the IGT engine or componentmodule, a much smaller compressor is required for producing thecompressed air than in the prior art engine test facilities. If a CAESfacility is not available, the engine or component module testing CAESfacility can be located near to an underground cavern (such as a saltdome) or large geologic cavern that can be used to store the compressedair. The compressor can be one-tenth of the size normally required tosupply this large of a volume of compressed air since the smallercompressor can be operated for a longer period of time (for example 72hours) to supply the required volume and pressure of compressed air inthe reservoir of the CAES or testing CAES facility. Thus, the cost ofequipment will be much lower since the larger and costlier compressor isnot required to produce this large of a volume and pressure ofcompressed air for the testing process. The storage caverns facility canalso be used to store gaseous fuels such as CH₄ or H₂ in the undergroundcavern or mine such as an old salt mine.

A high Mach number test can also be performed using the CAES facility orstorage cavern to store a vacuum (a negative pressure in relation toatmospheric pressure) within one of the caverns or mines. The largevolume of low pressure (vacuum) air can be used to vary a downstreampressure for the high Mach number testing of vehicles or engines in awind tunnel with a low capital equipment cost. The testing facility canbe connected to a high pressure cavern upstream and to a negativepressure cavern downstream in order to produce a very high pressuredifferential for the test facility in order to test an aero component.Or, instead of a vacuum chamber the lower pressure at the outlet of thetest object can be subjected to an ejector using the compressed air fromthe underground storage reservoir to produce a lower pressure.

For testing an industrial or aero gas turbine engine, the engine isconnected to drive multiple compressors each producing differentpressures and each being connected to a separate underground reservoirto hold the compressed air at different pressures. One reservoir mightbe used to store relatively low pressure compressed air, a secondreservoir might be used to store medium pressure compressed air, and athird reservoir might be used to store relatively high pressurecompressed air. When a testing phase requires a certain pressure of air,the reservoir with the minimum pressure can be used instead of wastingpressurized air that requires decreasing of the pressure.

The cost of the storage volume has always limited the test timeavailable from blow down tests and mass-flow rate during the test time.The prior art has always been to use relatively small manmade tanks forstoring the high pressure air or the vacuum. Prior art low pressurestorage tanks exist of around 50 meters in diameter that can store a lowpressure gas. For high pressure gases, a cylinder tank made of carbonfiber of about 36 inches in diameter can store up to 200 bar ofpressurized gas. The present invention is to use a man-made solutionmined cavern to form a very large underground cavern to store highlycompressed air for aerospace and gas turbine engine testing or componentmodule testing. A geographic salt dome cavern can be thousands of timelarger than the largest manmade tank and built using solution mining ata small fraction of the cost. The use of a single or multiple salt domecaverns or similar geographic cavern to store and release gases to andfrom a series of different cavern pressures can significantly reduce thecost of aerodynamic wind tunnel and gas turbine engine or componentmodule testing. The caverns can be mined at various depths to be bestadapted to meeting the storage pressure range requirement of aparticular cavern. In addition, flow conditions previously thoughtunaffordable therefore never previously available to the industry fortesting can now become part of the standard test protocol.

The underground compressed air storage reservoir and the test facilityfor testing a gas turbine engine or a component of an engine includes anon-vitiating heat exchanger to preheat the compressed air from thereservoir to produce non-vitiated compressed air for use in a testcomponent such as a combustor in order to more accurately test thecomponent. The heat exchanger can be electric or use fuel and air toproduce a hot gas that does not mix with the compressed air from thereservoir in order to preheat the compressed air to the requiredtemperature and pressure for testing the component without decreasingthe oxygen content of the compressed air.

In another embodiment of the present invention, the non-vitiating heatercan be replaced with an air turbine that is driven by compressed airfrom the underground storage reservoir, where the air turbine drives areal compressor that will produce the required compressed air at thedesign pressure and temperature that is burned with a fuel in acombustor for testing of the combustor. A compressor can also be testedwith this design in that the air turbine is used to drive the compressorduring the testing phase.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 shows a schematic view of a large gas turbine engine testfacility using an underground compressed air reservoir of the presentinvention.

FIG. 2 shows a schematic view of a compressed air energy storagefacility with a large frame heavy duty industrial gas turbine enginelocated nearly for testing of the engine or for testing a component of agas turbine engine of the present invention.

FIG. 3 shows a schematic view of a turbine component of an engine fortesting according to the present invention.

FIG. 4 shows a schematic view of a compressor component of an engine fortesting according to the present invention.

FIG. 5 shows a schematic view of a combustor component of an engine fortesting according to the present invention.

FIG. 6 shows a schematic view of an aero vehicle or aero componentwithin an air tunnel for testing according to the present invention.

FIG. 7 shows a schematic view of an engine testing facility of thepresent invention with a thermal heat storage device.

FIG. 8 shows a schematic view of an engine testing facility of thepresent invention with three separate compressed air reservoirs to holddifferent pressures of compressed air.

FIG. 9 shows an embodiment of the present invention in which anon-vitiated air heater is used to preheat the compressed air from thecavern prior to entering a test component.

FIG. 10 shows an embodiment of the present invention in which anelectric heater is used to preheat the compressed air in the FIG. 9embodiment.

FIG. 11 shows an embodiment of the present invention with a non-vitiatedair heater that uses a fuel to preheat the compressed air for the FIG. 8embodiment.

FIG. 12 shows an embodiment of the present invention for a high Machnumber test in which the preheated air from the non-vitiated air heaterin FIG. 11 is further heated by direct injection of a fuel into the hightemperature compressed air.

FIG. 13 shows another embodiment of the present invention wherecompressed air from the storage reservoir 13 is supplied to a heater 62to produce non-vitiated air that is delivered into a combustor 22.

FIG. 14 shows a variation of the test facility of FIG. 13 in which ahigh Mach number heater 81 is used between the non-vitiated compressedair heater 62 and the combustor 22 that is to be tested.

FIG. 15 shows another embodiment of the present invention in which atest facility can test a component such as a combustor at high altitudewhere the pressure of the air is low.

FIG. 16 shows another embodiment of the present invention in which thetest facility is used to test a component such as a combustor at a coldenvironment.

FIG. 17 shows another embodiment of the present invention in which thetest facility is used to test a compressor under normal operatingconditions.

FIG. 18 shows another embodiment of the present invention in which thetest facility is used to test a compressor under a cold environment suchas high altitude.

FIG. 19 shows another embodiment of the present invention in which thetest facility is used to test a turbine under warm air conditions.

FIG. 20 shows another embodiment of the present invention in which thetest facility is used to test a combustor at full load conditions.

FIG. 21 shows another embodiment of the present invention in which thetest facility is used to test a turbine at high altitude conditions.

FIG. 22 shows another embodiment of the present invention in which thefacility is used to testing a turbine at high altitude conditions wherethe turbine drives a generator as the load.

FIG. 23 shows another embodiment of the present invention in which anair turbine is used to drive a compressor to produce high pressure andhigh temperature compressed air for test of a combustor.

FIG. 24 shows another embodiment of the present invention in which anair turbine is used to drive a compressor for testing of a compressor.

FIG. 25 shows another embodiment of the present invention in which thetest facility is used to test a component such as a full-sized aircraftin a wind tunnel.

FIG. 26 shows a test facility according to one embodiment of the presentinvention using a storage reservoir such as an underground salt dome toprovide long duration, full scale combustor, augmenter, and hypersonicpropulsion system tests.

FIG. 27 shows a CAES (Compressed Air Energy Storage) test facility ofthe present invention with a cave fill process that includes a number ofcompressors and intercoolers and an after-cooler formed in series flowthat discharges into the cavern.

DETAILED DESCRIPTION OF THE INVENTION

A test facility and a process for testing a turbine or combustorcomponent module for an industrial or aero gas turbine engine is shownin FIG. 1 in which compressed air stored within a large undergroundcavern is used to supply the high flow rate and pressure required fortesting an engine or component module under normal engine operatingconditions. The engine or component module test facility includes asmall compressor 11 (small in relation to the compressor used on theactual gas turbine engine in which the combustor is being tested), anelectric motor (or a gas or diesel powered engine can be used) or asmall gas turbine engine 12 to drive the compressor 11, an undergroundcompressed air storage reservoir 13 to store compressed air from thecompressor 11, an air pressure regulator valve 14 to control thepressure released from the underground compressed air storage reservoir13, an air heater 15 to heat the compressed air flowing from thereservoir 13 to a temperature that would normally be passed into thecombustor of the actual engine, a fuel source 17 such as natural gas tobe burned with the compressed heated air, a combustor 16 that is to betested, a hot exhaust gas cooler 18 to cool the hot exhaust gas from thecomponent that is being tested, and an exhaust and silencer 19 todischarge the combustor exhaust. The heater 15 is a non-vitiating heaterthat will produce heated compressed air at a proper temperature fortesting in which the oxygen content is at a normal range for atmosphericair.

The compressed air storage reservoir 13 can be a pre-existingunderground storage facility such as an emptied salt cavern, or can beformed from a salt mine using a solution to create a cavity within thesalt mine capable of storing compressed air for engine or componentmodule testing. Or, if the engine testing facility is located at a CAESfacility, the storage reservoir for the CAES facility can be used as thecompressed air source for the engine or engine component testing. Thestorage reservoir 13 must be capable of storing enough compressed air ata high pressure and high flow rate so that the combustor can be properlytested. The smaller compressor 11 can be much smaller (such as aroundone-third the size of one of the larger compressor used in the prior arttest facilities. Instead of a compressor that cost $10-100 Million, thesmaller compressor used in the present invention would only cost around$1-10 Million. Also, since the storage tank 13 can be filled over a longperiod of time, the smaller compressor 11 can be operated for severaldays to fill the reservoir 13 with enough compressed air for the nexttest to be performed.

The pressure regulator valve 14 controls the release of the compressedair from the storage reservoir 13 that will flow into the combustor 16or test article for testing. Because the compressed air released fromthe storage reservoir 13 is relatively cold air, the air heater 15 willheat the compressed air to the normal temperature that would bedischarged from a required temperature for testing of the combustor orthe turbine or other component that is to be tested. Using a fuel todirectly heat the compressed air would supply heated compressed air butat a lower oxygen content.

The test facility of the present invention can be used to testcombustors of modern day engines that use the can-annular combustor orthe annular combustor or silo combustors. Aero engines typically use anannular combustor while industrial engines use an annular arrangement ofcan combustors commonly referred to as a can-annular combustor. In thecan-annular and annular combustors, to reduce the requirement of flowfor testing, these combustors are tested by using only a small sectionof the combustor because of the symmetry. However, some error isproduced even when testing of only a section of the combustor. Toproduce a full and accurate test of the combustor, the entire combustormust be tested for flow. For the silo type combustor, this combustorcannot be sectioned so that a portion of the combustor can be flowtested that would represent the entire combustor. To test the silo typecombustor or the aero annular combustor, the entire combustor should beflow tested and therefore a high flow rate is required. With thetremendous storage capability of the underground storage reservoirsystem of the present invention, full testing of the combustors of anytype can be performed using the required high flow rates and pressureswithout the high cost of the large compressors used in the prior artengine testing facilities and at much longer testing periods.

The combustor testing can be performed without burning a fuel in thecombustor, or can be tested under normal operating conditions by burningthe fuel as normal within the combustor by injecting the fuel throughthe injectors and into the combustor to be burned with the compressedair from the storage tank 13.

With the combustor test facility of the present invention, even an oldercombustor from an older engine can be tested in order to improve thecombustor performance. The older engines that used the silo type orannular type combustor would be idea for use with the much lower pricedtesting facility of the present invention. Modifications to thecombustor can be done and then tested at a lower cost such thatmodernizing these older combustors would be cost effective.

An apparatus and process for testing a large industrial or aero gasturbine engine or a single component module of an engine, where theengine testing facility is established close to a compressed air energystorage (CAES) facility so that the engine during testing can supply theCAES facility with compressed air, or the CAES facility can supply theengine testing facility with compressed air for the testing of an singleengine component is shown in FIG. 2. FIG. 2 shows a CAES facility(includes 41-46) which is located next to a large underground cavern orold salt mine 13 that can be used for storage of compressed air. Thetest engine includes a large industrial gas turbine engine with acompressor 21, a combustor 22 and a gas turbine 23 to produce mechanicalwork that is used to drive a compressor 24 to fill the cavern. Thecompressor 24 provides for a load to the engine during testing. At lowdemand for electrical power, the power plant can be used to drive acompressor 24 to produce compressed air to be stored within theunderground reservoir 13. However, unlike in the prior art, the load isnot wasted but converted into compressed air for storage in thereservoir 13. At peak demand, the stored compressed air is then suppliedto the power plant for later use. Air line (a) represents compressed airbeing discharged from the reservoir while air line (b) representscompressed air being delivered to the reservoir 13. Air line (c)represents a lower pressure air such as from a vacuum or an ejector. Avalve 35 is used to prevent compressed air from discharging from thereservoir 13 and back out through the compressor 24.

An IGT engine testing facility is located adjacent to the CAES facility(or cavern) so that the load from the engine that is being tested can beused to produce compressed air for storage in the CAES facility, and theCAES facility can be used to supply compressed air (or a vacuum) to theengine testing facility. With this association, the overall efficiencyof both the engine testing facility and the CAES facility will beimproved. A lower pressure can be produced using a storage reservoirwith a vacuum or a storage reservoir with compressed air connected to anejector that will be described below in more detail.

For testing of an IGT engine (FIG. 2), the gas turbine 23 is connectedto drive a compressor 24 so that the load from the engine during testingis used to drive the compressor 24 to produce compressed air that isthen stored within the CAES facility for use in peak power productionlater or for other engine testing requirements. Thus, no disruption tothe electric grid is produced, and no energy from the engine testing iswasted. Compressed air from the CAES facility can be burned with a fuelto produce the hot gas stream for running the CAES plant or for testingwithin the turbine, and the turbine can be used to drive a compressor toresupply the CAES facility for later use.

Another benefit of the testing facility of FIG. 2 for large enginesusing the compressed air energy storage reservoir 13 is that thereservoir 13 functions as a load damper in the case when the gas turbineengine trips.

The air storage reservoir 13 can be made very large in order to allowfor a large industrial or aero gas turbine engine to be tested for along period of time such as a few days and thus store the energy ascompressed air. The compressed air produced during this long period oftesting can then be used for process generation or other industrialapplications in addition to power generation.

Also seen in FIG. 2, the CAES testing facility can also include anelectric motor/electric generator 43 to drive a compressor 41 through aclutch 42 to resupply the reservoir 13 with compressed air. Or, thecompressed air stored within the reservoir 13 can be used to drive aturbine 46 thru a clutch 44 which drives the electric generator 43 toproduce electrical energy. An optional combustor 45 can be used to burnthe compressed air from the reservoir with a fuel and produce a hot gasstream that is then passed through the turbine 46 to produce electricenergy from the generator 43.

In the testing of a single engine component, such as a gas turbine inFIG. 3 or a compressor in FIG. 4 or a combustor in FIG. 5, the largevolume and high pressure compressed air can be supplied from the storagereservoir 13 of the CAES facility for use in testing these large gasturbine engine components or as a load on the test article such as thecompressor 24 that can resupply the storage reservoir 13. Therefore, alarge capital investment in equipment and a building is not requiredsince the infrastructure already exists at the CAES power plant. In FIG.3, compressed air from the storage reservoir 13 is used to drive the gasturbine 23 for testing. An optional combustor can also be used toproduce the hot gas stream and passed through the turbine to recreate anormal operating condition. A compressor 24 driven by the gas turbine 23during testing can be used to provide a load on the turbine 23 duringtesting that will also produce compressed air that can be resupplied tothe reservoir 13. A heat source 51 can be used to heat up the compressedair coming from the cavern 13. Compressed air from the reservoir can beused to drive an air turbine 23 that then drives the compressor 24 thatwill produce compressed air at a high pressure and a high temperaturefor testing a combustor 22 with the proper pressure and temperature ofthe compressed air without having to heat the compressed air from thereservoir 13. This design will eliminate the need for a non-vitiatingheater.

In FIG. 4, a compressor is tested under normal operating conditions fora long period of time. The compressor is driven by a motor, such as anelectric motor 31, and compresses air that is then stored within thecompressed air storage reservoir 13. In FIG. 5, a combustor is testedusing compressed air from the storage reservoir 13. Fuel is mixed andburned with the compressed air within the combustor for the testprocess.

Because of the use of an underground CAES facility for the supply ofcompressed air for testing the IGT or aero engine or components, a muchsmaller compressor is required for producing the compressed air than inthe prior art engine test facilities. The compressor can be one-third ofthe size normally required to supply this large of a volume ofcompressed air since the smaller compressor can be operated for a longerperiod of time (for example 72 hours) to supply the required volume andpressure of compressed air in the reservoir 13 of the CAES facility.Thus, the cost of equipment will be much lower since the larger andcostlier compressor is not required to produce this large of a volumeand pressure of compressed air for the testing process.

The CAES facility can also be used to store gaseous fuels such as CH₄ orH₂ in the underground cavern or mine such as an old salt mine. Thegaseous fuel can be compressed along with air and then used, forexample, to test a combustor by passing the compressed air and the fuelinto a combustor and ignited. The resulting hot gas stream is thenpassed through the gas turbine for testing.

A high Mach number test can also be performed using the CAES facility tostore a vacuum (FIG. 6) within the cavern or salt mine. The large volumeof negative pressure (vacuum) air or from an ejector can be used to varya pressure for the high Mach number testing of vehicles or engines in awind tunnel with a low capital equipment cost. A second reservoir can beused to store a vacuum (31 in FIG. 2) that can be used for testing acomponent in a wind tunnel as seen in FIG. 6. Or, the reservoir storingcompressed air can be used to operate an ejector that will produce alower pressure at the downstream side of the test article. Compressedair can be supplied to an inlet end of the tunnel from the storagereservoir through line (a) and a negative pressure (vacuum) can besupplied on the outlet end from the vacuum reservoir 31 or ejectorthrough line (c). The negative pressure reservoir 31 can be created byusing a vacuum pump to draw air out and produce the negative pressure.The vacuum pump can also be small and run for a long period of time tofill the vacuum reservoir 31 with negative pressure for testingpurposes. The negative pressure in the vacuum reservoir 31 can also beproduced by pumping hydrogen or oxygen into the reservoir 31 and thenpumping hydrogen or oxygen into the reservoir to combustor the oxygenand hydrogen mixture to produce water and a very low pressure thatresults from the conversion of a gas to a liquid. To produce therequired low pressure for certain testing, a vacuum pump can then beused to further decrease the vacuum reservoir pressure.

With the present invention, the large amounts of high pressure airrequired for full scale testing of large components such as a largeindustrial or aero gas turbine engine can be performed and at lowercosts than in the prior art. Also, engine components such as acombustor, a compressor or a gas turbine can also be tested. Full scaleaircraft testing can also be performed using a vacuum generated withinthe CAES facility to produce a high Mach number flow over the vehicle orpart. The CAES facility currently operated in McIntosh, Ala. orHuntsdorf, Germany would be an ideal location to locate the large enginetest facility of the present invention. However, any large volumeunderground reservoir from a salt mine or a coal mine could also be usedto store high pressure compressed air that could be required for testingof the engine or a single component of an engine. At the McIntosh, Ala.CAES facility, a source of hydrogen production is available and couldthen be used for testing of hydrogen combustors.

FIG. 7 shows another embodiment of the engine testing facility of thepresent invention in which a thermal heat storage device 36 is used tostore as much of the heat from the hot compressed air produced in thecompressor 24 that would pass into the storage reservoir 13 anddissipate therein after time due to heat transfer from the hot air tothe cooler walls of the storage reservoir 13. Heat from the hotcompressed air is stored and then passed into the colder compressed airthat is discharged from the reservoir 13 prior to be used in the testingprocess.

FIG. 8 shows another embodiment of the engine testing facility of thepresent invention in which multiple compressed air reservoirs are usedwith each reservoir holding a different pressure. The gas turbine engine(which includes a compressor 21, a combustor 22, and a turbine 23)drives a low pressure compressor 24 and a medium pressure compressor 25and a high pressure compressor 26. Each of the compressors 24-26 isconnected to a separate compressed air storage reservoir. The differentpressures are for use in different components or phases of operation ofa component or of an engine during all phases of testing. For example, alow pressure reservoir 13 could be used to store compressed air at 5 to10 bars, the medium pressure reservoir 28 could be used to storecompressed air at 10 to 30 bars, and the high pressure reservoir 29could be used to store compressed air at 50 to 100 bars. The use of thedifferent pressure reservoirs improves the efficient of the testingfacility in that high pressure air from the 50 to 100 bar reservoir isnot required for use in the low pressure testing component of around 5bar in which the pressure must be decreased from the high pressure tothe low pressure prior to use in the component to be tested. Also, theFIG. 8 embodiment can also be used to produce different loads during theengine testing process. When a low load is required, the engine can beused to drive the low pressure compressor 24. When a high load isrequired, the engine can be used to drive the high pressure compressor26. Or, a combination of compressors can be driven at the same time toprovide even higher loads to the engine.

In another embodiment of the underground salt mine, a brine solution canbe stored and used to drive an electric generator and produce electricalenergy. If water was used in a salt cavern, the water would dissolve thesalt walls of the cavern and function to melt away the cavern surface. Asalt brine solution that is saturated with salt will not dissolve awaythe salt cavern walls. Also, another advantage our using brine insteadof water is that when it is fully saturated with salt it has a specificgravity of 1.2 compared to water, therefore providing 20% more power forthe same size equipment. Two caverns are used with different elevationsso that a large pressure difference can be used for power production.For example, a first cavern would be located at 500 feet below thesurface while a second cavern would be located 1,500 feet below thesurface to produce a pressure head equal to 1,000 feet. The saturatedsalt brine solution could be pumped from the lower cavern during lowpower demand and into the higher elevation cavern for storage until peakdemand. At peak demand, the brine solution can be allowed to flow downand into the lower cavern through a turbine (such as a Francis turbine)that will be used to drive an electric generator and produce electricalenergy. Because of the higher specific gravity (compared to water) morepower can be extracted from the brine solution.

In another embodiment, instead of a salt cavern with a salt brinesolution, a petroleum storage cavern can be used for pressure head todrive the turbine and electric generator. Salt caverns are currentlyused for the US strategic petroleum reserve. The pumped storage facilitycould them be used for storage of fluid height potential energy fordaily use and chemical energy long term emergencies. The stored fuel oroil in a storage reservoir can be used to drive the turbine and electricgenerator. Fuel or oil in one reservoir can be pumped to a higherelevation during low demand and then discharged into a lower reservoirthrough a turbine to drive the electric generator during peak demand.

In another embodiment, the power from a large gas turbine engine duringtesting could be dissipated and stored by pumping a liquid (such as abrine solution) between two different elevations of caverns. Forexample, the turbine would be used to drive a pump that will pump abrine solution from a lower level cavern up to a higher level cavern todissipate the energy being produced by the engine. Then, the brinesolution can be passed through another turbine from the higher elevationto the lower elevation to drive the turbine and an electric generatorconnected to the turbine to produce electrical power. The turbine can beconnected to a Francis turbine through a speed reduction gear forpumping the fluid up to the higher elevation cavern or storagereservoir. The same or a second Francis turbine is then used to drivethe electric generator when the liquid flows down to the lower elevationcavern.

FIG. 9 shows an embodiment of the present invention used to test acomponent of a gas turbine engine, such as a combustor or a gas turbineusing compressed air from the underground cavern or reservoir 13. Inorder to properly test a component of a gas turbine engine such as acombustor, the compressed air that enters the combustor and is burnedwith a fuel must enter the combustor at the pressure and temperaturethat would normally be produced by a compressor operating with the gasturbine engine. Since the compressed air that is to be used for thetesting of the combustor is supplied from the cavern 13, this air mustbe preheated to the desired testing temperature. However, this preheatedair must not be burned with a fuel prior to entering the combustorbecause the compressed air would have less oxygen content than from thecompressor of the engine. Thus, a non-vitiated compressed air must beused in which no combustion has occurred. Otherwise, the testing of thecombustor would not be a real simulation and thus the results would beunreliable. Therefore, the relatively cool compressed air from thecavern 13 is preheated by a non-vitiating heater 62 that burns a fuelwith atmospheric air that is passed over a closed tube in which thecompressed air from the cavern is passed in order to transfer heat tothe compressed air and produce a hot high pressure compressed air thatis then delivered to the test component such as a combustor. With thehot compressed air entering the combustor, a fuel can then be burned tosimulate the gas turbine engine and test the combustor under realconditions. A flow control valve 61 is used to control the amount ofcompressed air delivered from the cavern to the preheater 62. A pressurecontrol valve 64 is used to control the pressure in the test component63. The exhaust 67 from the test component can be injected with water 66to cool down the exhaust prior to discharge from the test facility.

FIG. 10 shows an electric heater 65 that can be used to preheat thecompressed air from the cavern 13 to produce the non-vitiated compressedair for use in the testing component 63 instead of the fuel burning withair.

FIG. 11 shows an embodiment of a non-vitiated compressed air preheaterthat is used in the present invention of FIG. 9. Compressed air from thecavern 13 at 2,000 psi and 200 degrees F. enters the preheater at 71 andflows toward the exit 72. Compressed air also from the cavern 13 entersa second inlet of the preheater at 2,050 psi and 200 degrees F. at 73and flows toward a section where a fuel is injected to burn with thesecond flow of compressed air to produce compressed air at 3,000 degreesF. This hotter compressed air at 3,000 degrees F. is then used topreheat the first flow of compressed air from 200 degrees F. to 2,100degrees F. that exits the preheater at 72. The second flow is dischargedto the atmosphere at 75. The pressures and temperatures displayed forFIG. 11 are for a certain size aircraft engine component but can be atdifferent pressures and temperatures depending upon what component areto be tested.

FIG. 12 shows an embodiment of the non-vitiated compressed air preheaterthat is used for a test in which the compressed air must be furtherheated to a temperature such as 2,800 degrees F. After exiting thepreheater at 72, the non-vitiated compressed air at 2,100 degrees F. isburned with a fuel to produce a temperature of 2,800 degrees F. at theoutlet 76. It is very difficult to heat air past around 1,500 degrees F.with an externally fired heater due to high pressure gradients acrossthe heater tubes and high temperature of the tubes. The test facility ofthe present invention allows for temperatures of 2,100 degrees F. fornon-vitiated air and 2,800 degrees F. for partially vitiated air. Sincethe flows through 74 and 71 are both at high pressure, the surface area71/74 of the heat exchanger tubes or tube can be greatly reducedcompared to a conventional natural gas heater in which the hot gas is atatmospheric pressure. The tube life is also increased since the pressuregradient across the tube wall is reduced.

FIG. 13 shows another embodiment of the present invention wherecompressed air from the storage reservoir 13 is supplied to a heater 62to produce non-vitiated compressed air that is delivered into acombustor 22. A pressure regulator valve 61 controls the amount ofcompressed air delivered from the storage reservoir 13. Fuel and air isburned within the heater 62 to produce a hot gas that is used to heat upthe compressed air from the storage reservoir 13 without decreasing itsoxygen content so that the compressed air delivered to the combustor 22is at the temperature and pressure that would normally be dischargedfrom a compressor that would feed to the combustor 22 of the gas turbineengine. The non-vitiated compressed air would have normal oxygen contentbecause no fuel is burned directly within the compressed air. Water canbe injected into the exhaust from the combustor 22 in order to cool thehot exhaust prior to discharge to the atmosphere. With the combustortest facility of the present invention, a combustion chamber can betested at the component level, and at full scale, and for a longduration, and with a low cost compared to that available in the priorart.

FIG. 14 shows a variation of the test facility of FIG. 13 in which ahigh Mach number heater 81 is used between the non-vitiated compressedair heater 62 and the combustor 22 that is to be tested. The heater 81would be a high enthalpy heater. The FIG. 14 embodiment is used to testa combustor or other component at a high Mach number by furtherincreasing the inlet temperature of the non-vitiated compressed air andthus simulate the conditions at an inlet to a component of an aircrafttraveling at a high Mach number.

In FIG. 15, another embodiment of the present invention shows a testfacility that can test a component such as a combustor at high altitudewhere the ambient outside pressure of the air is low. The FIG. 15 testfacility is similar to the FIG. 14 test facility, but with the additionof an ejector 82 positioned downstream from the test article such as thecombustor 22. The combustor 22 would discharge into a low pressureatmosphere at high altitude and thus the discharge pressure for testingshould also be low. The ejector is supplied with compressed air from thestorage reservoir 13 that is discharged into the exhaust gas from thecombustor 22 and decreases the pressure. The ejector 82 functions like ajet pump in that a first gas is discharged into a second gas and pullsthe second gas forward, resulting in the inlet of the second gas todecrease in pressure. The non-vitiated compressed air is delivered tothe combustor 22 and burned with a fuel to produce a hot gas stream thatis exhausted from the combustor. The compressed air from the storagereservoir 13 is discharged into the combustor exhaust gas to decreasethe pressure and thus simulate the combustor conditions at highaltitude.

In FIG. 16, the test facility is used to test a component such as acombustor at a cold environment. Compressed air from the storagereservoir 13 is delivered to an air turbine 84 that will discharge thecompressed air at lower temperature into a combustor 22 that is thenburned with a fuel to test the combustor under cold conditions at inlet.A flow regulator valve 61 controls the pressure and flow into the airturbine 84. In an air turbine, no combustion occurs, only a decrease inthe pressure and temperature of the air. In an example, compressed airenters the air turbine at 30 degrees C. and is discharged at −120degrees C.

In FIG. 17, the test facility is used to test a compressor under normaloperating conditions. Compressed air from the storage reservoir 13 isdelivered to a non-vitiated heater 62 to increase the temperature of thecompressed air to a normal inlet temperature for the compressor beingtested. Compressed air from the storage reservoir 13 is also deliveredto an air turbine 84 that is used to drive the compressor 24 beingtested. Pressure regulator valves 61 are used to control compressed airflows into the heater 62 and the air turbine 84. An advantage of theFIG. 17 test facility is quick on and off control which results inlittle to no upset of the electrical grid. Also, large compressors canbe tested with full scale operation. A bypass line with a pressureregulator valve 61 from the storage reservoir 13 to an inlet of thecompressor 24 can be used to vary an inlet pressure or temperature ofthe air into the compressor 24 to test for varying inlet conditions.

In FIG. 18, the test facility is used to test a compressor under a coldenvironment such as high altitude. The compressor 24 being tested isdriven by an air turbine 84 using compressed air from the storagereservoir 13. Compressed air from the storage reservoir 13 is alsodelivered to a second air turbine 85 that decreases the pressure andtemperature of the compressed air that is then delivered to an inlet ofthe compressor 24 being tested. The second air turbine 85 can drive anelectric generator 86 to produce electricity for use elsewhere. Thecompressed air from the compressor 24 being tested can be delivered backto the storage reservoir 13 or elsewhere for use in another test. Inanother version of the FIG. 18 embodiment used to test a compressor, theair turbine exhaust could be used as the inlet air into the compressor.This would provide a lower pressure and a lower temperature of inlet airfor the compressor 24 being tested while the air turbine 84 is stillused to drive the compressor 24.

In FIG. 19, the test facility is used to test a turbine under warm airconditions. Compressed air from the storage reservoir 13 is delivered toa non-vitiated heater 62 to increase the temperature of the compressedair to a warm condition and passed through the turbine 23 withoutburning a fuel. The heater 62 can be a non-vitiated heater or a ductburner. The warm compressed air can be used to test the turbine 23 foraerodynamic and cooling data. The turbine 23 can drive a load 87 such asa compressor or a generator.

The test facility is FIG. 20 is used to test a combustor at full loadconditions. Compressed air from the storage reservoir 13 is delivered toa non-vitiated heater 62 to increase the temperature of the compressedair to simulate the conditions that would be discharged from acompressor sized for the combustor that is being tested. Fuel and airare burned to produce heat that is then used to heat up the compressedair within affecting the oxygen content. The preheated compressed air isthen delivered to the combustor 22 where the air is burned with a fuelto produce a hot gas that is discharged to the turbine 23 that is beingtested. The turbine 23 can drive a load 87 such as a compressor or agenerator. A large industrial engine turbine can be tested at full loadconditions for many hours using this test facility.

FIG. 21 shows a test facility for testing a turbine at high altitudeconditions. Compressed air from the storage reservoir 13 is heatedthrough a non-vitiated heater 62 and then passed through the gas turbine23 that is being tested. Compressed air from the storage reservoir 13 isalso delivered to an ejector 82 that lowers an outlet pressure of theturbine 23 exhaust to simulate high altitude conditions on the dischargeend of the turbine 23. The turbine 23 can drive a load such as acompressor 24 or a generator. At high altitude, the air has a lowerReynold's number and thus can cause separation in the low pressureturbine. Thus, testing can in the facility of FIG. 21 can improve thedesign of the turbine at high altitudes. FIG. 22 shows a facility fortesting a turbine at high altitude conditions where the turbine 23drives a generator 86 as the load.

In the FIG. 23 embodiment, a non-vitiating heater can be eliminated fromthe combustor testing option. Compressed air from the reservoir 13 canbe supplied to an air turbine 23 that will drive a compressor 24 toproduce the proper compressed air with the pressure and temperaturerequired for discharge into the combustor 22 that is to be tested. Thus,the high pressure and high temperature compressed air is produced froman actual compressor that is sized for use with the combustor 22 that isto be tested. In the FIG. 24 embodiment, the air turbine 23 is used todrive a compressor 24 that is being tested.

The test facility shown in FIG. 25 is used to test a component such as afull-sized aircraft in a wind tunnel. A component to be tested issecured within a wind tunnel 88. Compressed air from the storagereservoir 13 can be passed through a non-vitiated heater 62 to increasethe temperature of the compressed air delivered to the wind tunnel 88,or compressed air from the storage reservoir 13 can be passed through anair turbine 84 to decrease the temperature of the compressed air fordelivery to the wind tunnel 88. The air turbine 84 could be replacedwith a throttling valve that would lower the pressure and temperature ofthe compressed air from the storage reservoir 13. Compressed air fromthe storage reservoir 13 can also be delivered to an ejector 82 locateddownstream from the wind tunnel 88 to decrease the exit pressure at thewind tunnel 88. The ejector 82 functions to decrease the pressure of theair at the discharge end of the wind tunnel 88. With the ejector 82 atthe discharge end of the wind tunnel 88, very high Mach number tests canbe done on a component and for long periods of time compared to thatavailable in the prior art. The huge amount of compressed air availablewithin the storage reservoir 13 can be used to supply a large volume ofcompressed air to the wind tunnel. With the test facility of FIG. 23, avehicle can be tested at full scale and at high Mach numbers (Mach 5 toMach 10) and for hours and not seconds as is the current conditions ofthe prior art.

FIG. 26 shows a test facility using a storage reservoir such as anunderground salt dome to provide long duration, full scale combustor,augmenter, and hypersonic propulsion system tests. The benefits to thistest facility over the existing prior art text facilities is a 10 hourtest time versus around 60 seconds test time in the prior art. Also,lower operating costs are possible due to night-time electric rates andzero electric demand charges. A significantly lower capital cost isachieved due to a compression system cost reduced by 80% and a powerinfrastructure reduced. The test facility of the present invention canprovide for aero testing with a nominal flow rate of 500 lbs/second at apressure of 1,100 psi and a temperature of 1,450 degrees F. the testfacility of the present invention can provide for hyper testing with anominal flow rate of 1,000 lbs/second at a pressure of 2,800 psi and atemperature of 2,050 degrees F.

FIG. 27 shows a CAES (Compressed Air Energy Storage) test facility ofthe present invention with a cave fill process that includes a number ofcompressors 91 and intercoolers 92 and an after cooler 93 formed inseries flow that discharges into the cavern 13. The intercoolers 92 andthe after cooler 93 decrease the compressor 91 exit temperatures.Control valves 94 and 95 regulate the flow into and out of the cavern13. An externally fired heat exchanger 96 increases the temperature ofthe compressed air form the cavern 13 and delivers the heated compressedair to the test cell 97. Hypersonic and aerospace testing can beachieved with large volumes of compressed air and at much longer periodsof testing than is available in the current prior art test facilities.

We claim the following:
 1. A process for testing an aerospace vehicle orcomponent under low atmospheric conditions comprising the steps of:filling a first underground storage reservoir with compressed air;forming a vacuum in a second underground storage reservoir; securing anaerospace vehicle or component to be tested within a wind tunnel;passing compressed air from the first underground storage reservoir intothe wind tunnel for testing; and, applying a vacuum from the secondunderground storage reservoir to a downstream side of the wind tunnel.2. The process for testing an aerospace vehicle or component of claim 1,and further comprising the step of: the aerospace vehicle is a full sizeaircraft vehicle.
 3. The process for testing an aerospace vehicle orcomponent of claim 1, and further comprising the step of: the aerospacecomponent is a rocket engine.